Cardboard/paper piece on Dash 6V regulator

It's original. It's on the 12v input wire to the voltage limiter and tries to keep the power from jumping right to ground on the case. Best thing to do is to reuse it when you replace the limiter. Replace it with a modern voltage limiter from RTE - when you do you can just eliminate the capacitor. The old ones have points inside like an old distributor.